Semiconductor device and driving method of the same

ABSTRACT

The present invention provides a semiconductor device including a memory that has a memory cell array including a plurality of memory cells, a control circuit that controls the memory, and an antenna, where the memory cell array has a plurality of bit lines extending in a first direction and a plurality of word lines extending in a second direction different from the first direction, and each of the plurality of memory cells has an organic compound layer provided between the bit line and the word line. Data is written by applying optical or electric action to the organic compound layer.

TECHNICAL FIELD

The present invention relates to a semiconductor device and a method fordriving the semiconductor device.

BACKGROUND ART

In recent years, individual recognition technology has gotten a lot ofattention. For example, there is a technology to be used for productionand management, in which information such as a history of the object isclarified by giving an ID (an individual recognition number) to anindividual object. Above all, the development of semiconductor devicesthat send and receive data without contact by using an electromagneticfield or a radio wave have been advanced. As such semiconductor devices,in particular, a wireless chip (also referred to as an ID tag, an ICtag, and IC chip, an RF (Radio Frequency) tag, a wireless tag, anelectronic tag, or an RFID (radio Frequency Identification)) isbeginning to be introduced into companies, markets, and the like.

Many of semiconductor devices that have been already been put topractical use have a circuit using a semiconductor substrate (alsoreferred to as an IC (Integrated Circuit) chip) and an antenna, and theIC chip includes a memory and a control circuit.

In addition, depending on the structure of a memory provided in the ICchip, ways such as writing or reading of information are classified intovarious methods. For example, in the case of using a mask ROM for amemory circuit, no writing of data can be carried out other than inmanufacturing the chip. In this case, no writing of data can be carriedout other than in manufacturing the chip, and the chip is thus notuser-friendly. Therefore, an ID chip in which data can be written otherthan in manufacturing the chip has been needed.

On the other hand, in the case of using an EEPROM or the like for amemory circuit, while a user can freely rewrite the content, some oneother than the user is allowed to rewrite the information so thatfalsification is possible (for example, Non-Patent Document 1).Therefore, security measures are not implemented sufficiently now, andthus, measures that are able to prevent falsification by rewriting orthe like have been needed.

In addition, an element has been needed, and active research anddevelopment are carried out actively.

(Non-Patent Document 1)

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DISCLOSURE OF INVENTION

It is an object of the present invention to provide a semiconductordevice in which data can be written other than in manufacturing thesemiconductor device and falsification by rewriting can be prevented.Further, it is an object of the present invention to an inexpensivesemiconductor device that is easily formed and includes a memory elementand a method for driving the semiconductor device.

In order to achieve the objects, the present invention provides thefollowing.

A semiconductor device according to the present invention includes aplurality of bit lines extending in a first direction, a plurality ofword lines extending in a second direction that is different from thefirst direction, a memory cell array comprising a plurality of memorycells provided at an intersecting portion of the bit line and the wordline, and an organic memory element provided in the memory cell, wherethe organic memory element has a laminated structure of the bit line, anorganic compound layer, and the word line.

Further, another semiconductor device according to the present inventionincludes a plurality of bit lines extending in a first direction, aplurality of word lines extending in a second direction that isdifferent from the first direction, a memory cell array comprising aplurality of memory cells provided at an intersecting portion of the bitline and the word line, an organic memory element provided in the memorycell, and an antenna, where the organic memory element has a laminatedstructure of the bit line, an organic compound layer, and the word line.

In addition, in each of the semiconductor devices according to thepresent invention, at least one of the bit line and the word line is alight-transmitting property.

Further, another semiconductor device according to the present inventionincludes a plurality of bit lines extending in a first direction, aplurality of word lines extending in a second direction that isdifferent from the first direction, and a memory cell array comprising aplurality of memory cells surrounded by the bit lines and the wordlines, wherein the memory cell includes a transistor and an organicmemory element electrically connected to the transistor, and wherein theorganic memory element has an organic compound layer provided between apair of conductive layers.

Further, another semiconductor device according to the present inventionincludes a plurality of bit lines extending in a first direction, aplurality of word lines extending in a second direction that isdifferent from the first direction, a memory cell array comprising aplurality of memory cells surrounded by the bit lines and the wordfines, and an antenna, wherein the memory cell includes a transistor andan organic memory element electrically connected to the transistor, andwherein the organic memory element has an organic compound layerprovided between a pair of conductive layers.

In addition, in each of the semiconductor devices according to thepresent invention, at least one of the pair of conductive layers is alight-transmitting property.

In addition, in each of the semiconductor devices according to thepresent invention, the organic memory element has a resistanceirreversibly changed by writing.

In addition, in each of the semiconductor devices according to thepresent invention, a distance between the electrodes of the organicmemory element is changed by writing.

In addition, in each of the semiconductor devices according to thepresent invention, the organic compound layer comprises one of anelectron transporting material and a hole transporting material.

In addition, in each of the semiconductor devices according to thepresent invention, the organic compound layer has an electricconductivity that is 10⁻¹⁵ S/cm or more and 10⁻³ S/cm or less.

In addition, in each of the semiconductor devices according to thepresent invention, the organic compound layer has a film thickness of 5to 60 nm.

A method for driving a semiconductor device according to the presentinvention, where the semiconductor device comprises a plurality of bitlines extending in a first direction, a plurality of word linesextending in a second direction that is different from the firstdirection, a memory cell array comprising a plurality of memory cellsprovided at an intersecting portion of the bit line and the word line,and an organic memory element provided in the memory cell, where theorganic memory element comprises an organic compound layer providedbetween the bit line and the word line, where writing of data is carriedout by applying a voltage between the bit line and the word line tochange an electric resistance of the organic memory element, and wherereading of data is carried out by applying a voltage between the bitline and the word line to read the electric resistance of the organicmemory element.

Another method for driving a semiconductor device according to thepresent invention, where the semiconductor device comprises a pluralityof bit lines extending in a first direction, a plurality of word linesextending in a second direction that is different from the firstdirection, and a memory cell array comprising a plurality of memorycells surrounded by the bit lines and the word lines, where the organicmemory element comprises an organic compound layer provided between apair of electrodes, where writing of data is carried out by applying avoltage between the pair of electrodes to change an electric resistanceof the organic memory element, and where reading of data is carried outby applying a voltage between the pair of electrodes to read theelectric resistance of the organic memory element.

In accordance with the present invention, it is possible to obtain asemiconductor device in which data can be written (write once read many)other than in manufacturing the semiconductor device and falsificationby rewriting can be prevented. Further, it is possible to provide aninexpensive semiconductor device and a method for driving thesemiconductor device by providing a memory using an organic compoundthat is easily deposited as a material or a semiconductor deviceincluding the memory.

Furthermore, it is possible to provide a semiconductor device includinga memory element in which data can be written with small power.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are diagrams illustrating a semiconductor deviceaccording to the present invention and a method for driving thesemiconductor device;

FIGS. 2A to 2D are diagrams illustrating a semiconductor deviceaccording to the present invention and a method for driving thesemiconductor device;

FIGS. 3A and 3B are diagrams illustrating a semiconductor deviceaccording to the present invention;

FIGS. 4A to 4D are diagrams illustrating examples of a process formanufacturing a semiconductor device according to the present invention;

FIGS. 5A to 5D are diagrams illustrating a semiconductor deviceaccording to the present invention;

FIGS. 6A to 6C are diagrams illustrating a semiconductor deviceaccording to the present invention;

FIGS. 7A to 7H are diagrams illustrating usage patterns of asemiconductor device according to the present invention;

FIGS. 8A and 8B are diagrams illustrating usage patterns of asemiconductor device according to the present invention;

FIGS. 9A and 9B are diagrams illustrating a semiconductor deviceaccording to the present invention and a method for driving thesemiconductor device;

FIGS. 10A to 10C are diagrams illustrating a semiconductor deviceaccording to the present invention and a method for driving thesemiconductor device;

FIG. 11 is a diagram illustrating a semiconductor device according tothe present invention and a method for driving the semiconductor device;

FIG. 12 is diagram illustrating an example of a laser irradiation systemaccording to the present invention according to the present invention;

FIG. 13 is a diagram of measuring current-voltage characteristics of anorganic memory element in a semiconductor device according to thepresent invention;

FIG. 14 is a diagram of measuring current-voltage characteristics of theorganic memory element in a semiconductor device according to thepresent invention;

FIG. 15 is a diagram illustrating a semiconductor device according tothe present invention;

FIGS. 16A and 16B are respectively an optical microscope image and apattern diagram of a semiconductor device according to the presentinvention;

FIG. 17 is a diagram showing write characteristics of the semiconductordevice according to the present invention;

FIGS. 18A and 18B are diagrams showing current-voltage characteristicsof semiconductor devices according to the present invention;

FIGS. 19A and 19B are an optical microscope image and a cross-sectionalTEM image of an organic memory element according to the presentinvention after writing of data;

FIGS. 20A and 20B are cross-sectional TEM images of the organic memoryelement according to the present invention after the writing of data;

FIG. 21 is an optical microscope image of the organic memory elementaccording to the present invention after the writing of data;

FIGS. 22A and 22B are cross-sectional TEM images of the organic memoryelement according to the present invention after the writing of data;

FIG. 23 is a cross-sectional TEM image of the organic memory elementaccording to the present invention before the writing of data;

FIGS. 24A and 24B are diagrams showing current-voltage characteristicsof organic memory elements according to the present invention;

FIGS. 25A and 25B are diagrams showing current-voltage characteristicsof organic memory elements according to the present invention;

FIGS. 26A and 26B are diagrams showing current-voltage characteristicsof organic memory elements according to the present invention;

FIGS. 27A to 27F are diagrams illustrating the structures of organicmemory elements according to the present invention as examples;

FIGS. 28A and 28B are diagrams illustrating a semiconductor deviceaccording to the present invention;

FIGS. 29A to 29C are diagrams illustrating the semiconductor deviceaccording to the present invention;

FIG. 30 is a diagram showing current-voltage characteristics of anorganic memory element according to the present invention; and

FIG. 31 is a diagram showing writing voltages and characteristics beforeand after writing of the samples 1 to 6.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment modes of the present invention will be described below withreference to the accompanying drawings. However, the present inventionis not limited to the following descriptions, and it is to be easilyunderstood that various changes and modifications will be apparent tothose skilled in the art unless such changes and modifications departfrom the scope of the present invention. Therefore, the presentinvention is not to be construed with limitation to what is described inthe embodiment modes. It is to be noted that the reference numeral thatdenotes the same object is used in common between different drawings inthe following embodiment modes of the present invention.

Embodiment Mode 1

A semiconductor device 20 described in the present embodiment mode has afunction of non-contact exchange of data, and includes a power supplycircuit 11, a clock generation circuit 12, a datademodulation/modulation circuit 13, a control circuit 14 that controlsother circuits, an interface circuit 15, a memory 16, a data bus 17, andan antenna 18 (an antenna coil) (FIG. 1A). The power supply circuit 11is a circuit that generates various power sources to be supplied to eachcircuit in the semiconductor device 20, based on input analternating-current signal from the antenna 18. The clock generationcircuit 12 is a circuit that generates various clock signals to besupplied to each circuit in the semiconductor device 20, based on inputan alternating-current signal from the antenna 18. The datademodulation/modulation circuit 13 has a function ofdemodulating/modulating data for exchange with a reader/writer 19. Thecontrol circuit 14 has a function of controlling the memory 16. Theantenna 18 has a function of sending and receiving electromagneticfields or radio waves. The reader/writer 19 controls communication withthe semiconductor device 20 and processing of the data. It is to benoted that the semiconductor device 20 is not limited to the describedabove, and for example, another element such as a power supply voltagelimiter circuit or hardware for processing codes only may be added tothe structure described above.

Further, in FIG. 1A, the memory 16 has a feature of having a structure(hereinafter, also referred to as “an organic memory element”) in whicha layer including an organic compound (hereinafter, also referred to as“an organic compound layer”) is provided between a pair of conductivelayers. The memory 16 may include not only a memory composed of anorganic memory element but also other memories. The other memoriesinclude, for example, one or more memories selected from the groupconsisting of a DRAM, an SRAM, a FeRAM, a mask ROM, a PROM, an EPROM, anEEPROM, and a flash memory.

The memory including the organic memory element (hereinafter, alsoreferred to as “an organic memory”) uses an organic compound material,and the electrical resistance of the organic memory element is changedby applying optical or electric action to the organic compound layer.

Next, the structure of an organic memory will be described (FIG. 1B).The organic memory includes a memory cell array 22 in which a memorycell 21 including an organic memory element is provided in a matrix,decoders 23 and 24, a selector 25, and a read/write circuit 26.

The memory cell 21 includes a first conductive layer connected to a bitline Bx (1≦x≦m), a second conductive layer connected to a word line Wy(1≦y≦n), and an organic compound layer. The organic compound layer isprovided between the first conductive layer and the second conductivelayer.

Next, for the case of manufacturing the memory cell array 22 actually,the top-view structure and cross-sectional structure thereof will bedescribed (FIGS. 2A and 2B). It is to be noted that the memory cellarray 22 on a substrate 30 with an insulating surface includes firstconductive layers 27 extending in a first direction, second conductivelayers 28 extending in a second direction perpendicular to the firstdirection, and organic compound layers 29. The memory cell 21 isprovided at an intersection portion of the first conductive layer 27 andthe second conductive layer 28. The first conductive layers 27 and thesecond conductive layers 28 are provided like stripes to intersect witheach other. An insulating layer 33 is provided between the adjacentorganic compound layers 29. In addition, an insulating layer 34 thatserves as a protective film is provided to have contact with the secondconductive layers 28.

As the substrate 30, a glass substrate, a flexible substrate, a quartzsubstrate, a silicon substrate, a metal substrate, a stainless-steelsubstrate, or the like is used. A flexible substrate refers to asubstrate that is flexible and can be bent, and includes, for example, aplastic substrate including polycarbonate, polyalylate,polyethersulfone, or the like. The first conductive layers 27 and thesecond conductive layers 28 are formed with the use of a knownconductive material such as aluminum (Al), copper (Cu), and silver (Ag).

In the case of writing data an organic memory by light, one or both ofthe first conductive layers 27 and the second conductive layers 28 havea light-transmitting property. A light-transmitting conductive layer isformed with the use of a transparent conductive material such as indiumtin oxide (ITO), or formed with the use of a conductive material that isnot transparent to have a thickness that is able to transmit light.

For the organic compound layers 29, conductive (preferably, the electricconductivity is 10⁻¹⁵ S/cm or more and 10⁻³ S/cm or less) organiccompound materials can be used, and highly hole transporting materials,for example, aromatic amine (that is, having a benzene ring-nitrogenbond) compounds such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl(abbreviation: α-NPD),4,4′-bis[N-(3-methylphenyl)-N-phenylamino]-biphenyl (abbreviation: TPD),4,4′,4″-tris(N,N-diphenylamino)-triphenylamine (abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]-triphenylamine(abbreviation: MTDATA), and 4,4′-bis(N-(4-(N,N-di-m-tolylamino)phenyl)-N-phenylamino)biphenyl (abbreviation: DNTPD), phthalocyaninecompounds such as phthalocyanine (abbreviation: H₂PC), copperphthalocyanine (abbreviation: CuPc), and vanadyl phthalocyanine(abbreviation: VOPC), and the like can be used.

In addition, highly electron transporting materials can be used as theorganic compound materials, for example, materials including a metalcomplex having a quinoline skeleton or a benzoquinoline skeleton, suchas tris(8-quinolinolato) aluminum (abbreviation: Alq₃),tris(4-methyl-8-quinolinolato) aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato) beryllium (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum (abbreviation:BAlq), and materials such as metal complexes having an oxazole ligand ora thiazole ligand, such as bis[2-(2-hydroxyphenyl)benzoxazolato]zinc(abbreviation: Zn(BOX)₂) or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc(abbreviation: Zn(BTZ)₂), can also be used. Further, in addition tometal complexes, compounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene(abbreviation: OXD-7),3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), and bathophenanthroline (abbreviation: BPhen)can be used.

Further, the organic compound materials include4-dicyanomethylene-2-methyl-6[2(1,1,7,7-tetramethyljulolidine-9yl)ethenyl]-4H-pyran (abbreviation: DCJT),4-dicyanomethylene-2-t-butyl-6-[2(1,1,7,7-tetramethyljulolidine-9-yl)ethenyl-4H-pyran(abbreviation: DCJTB), periflanthene, 2,5-dicyano-1,4bis[2-(10-methoxy-1,1,7,7-tetramethyljulolidine-9-yl) ethenyl]benzene,N,N′-dimethylquinacridone (abbreviation: DMQd), coumarin 6, coumarin545T, 9,9′-bianthryl, 9,10-diphenylanthracene (abbreviation: DPA),9,10-bis(2-naphthyl) anthracene (abbreviation: DNA), and2,5,8,11-tetra-t-butylperylene (abbreviation: TBP). In addition, as amaterial that serves as a matrix when a layer in which the luminescentmaterial mentioned above is dispersed is formed, anthracene derivativessuch as 9,10-di(2-naphthyl)-2-tert-butylanthracene (abbreviation:t-BuDNA), carbazole derivatives such as 4,4′-bis(N-carbazolyl)biphenyl(abbreviation: CBP), metal complexes such as bis[2-(2-hydroxyphenyl)pyridinato]zinc (abbreviation: Znpp₂) andbis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: ZnBOX, and thelike can be used, and further, tris(8-quinolinolato) aluminum(abbreviation: Alq₃), 9,10-bis(2-naphthyl) anthracene (abbreviation:DNA), bis(2-methyl-8-quinolinolato)-4 phenylphenolato-aluminum(abbreviation: BAlq), and the like can be used.

Furthermore, as a material for the organic compound layers 29, amaterial can be used so that the electrical resistance of an organicmemory element is changed by applying optical or electric action. Forexample, a conjugated polymer doped with a compound (photoacidgenerator) that generates acid by absorbing light can be used, wherepolyacetylene group, polyphenylenevinylene group, polythiophene group,polyaniline group, polyphenyleneethylene group, and the like can be usedas the conjugated polymer. In addition, as the photoacid generator,arylsulfonium salt, aryliodonium salt, o-nitrobenzyltosylate,arylsulfonic acid p-nitrobenzylether, sulfonylacetophenone group,Fe-arene complexes PF₆ salt, and the like can be used.

In addition, a rectifying element may be provided between the firstconductive layer 27 and the organic compound layer 29 or between thesecond conductive layer 28 and the organic compound layer 29 (refer toFIG. 2D). A rectifying element typically indicates a schottky diode, aPN junction diode, a PIN junction diode, or a transistor that has a gateelectrode and a drain electrode connected to each other. Of course, adiode that has another structure may be provided. FIG. 2D shows a casein which a PN junction diode including semiconductor layers 44 and 45 isprovided between the first conductive layer 27 and the organic compoundlayer 29. One of the semiconductor layers 44 and 45 is an N-typesemiconductor, and the other is a P-type semiconductor. As describedabove, the selectivity of a memory cell and the operation properties ofreading and writing can be improved by providing a rectifying element.

In addition, as shown in FIG. 15, a memory 282 including an organiccompound layer provided between a pair of conductive layers can beprovided over an integrated circuit 281. Namely, the integrated circuit281 may be provided over a substrate 280, and the memory 282 may beformed thereover.

As described above, the organic memory element described in the presentembodiment mode has a simple structure in which an organic compoundlayer is provided between a pair of electrodes. Therefore, themanufacturing process thereof is simple, and providing inexpensivesemiconductor devices is thus made possible. In addition, the organicmemory described in the present embodiment mode is a nonvolatile memory.Therefore, it is not necessary to incorporate a battery for holdingdata, and thus, small, thin, and lightweight semiconductor devices canbe provided. Further, since the electric resistance of the organicmemory element is irreversibly changed by writing, rewriting of data isnot possible while writing of data (write once read many) is possible.Accordingly, it is possible to provide a semiconductor device for whichfalsification is prevented and security is ensured.

Next, operation in writing of data into the organic memory will bedescribed. Writing of data is carried out by optical action or electricaction. First, a case of carrying out writing of data by electric actionwill be described (refer to FIG. 1B). It is to be noted that the writingis carried out by changing an electronic property of the memory cell,where the initial state (a state without electric action applied) of thememory cell is data “0”, and a state with the electronic propertychanged is data “1”.

In the case of writing data “1” in the memory cell 21, the memory cell21 is first selected by the decoders 23 and 24 and the selector 25.Specifically, a predetermined voltage V2 is applied to the word line W3connected to the memory cell 21 by the decoder 24. Further, the bit lineB3 connected to the memory cell 21 is connected to the read/writecircuit 26 by the decoder 23 and the selector 25. Then, a write voltageV1 is output from the read/write circuit 26 to the bit line B3. In thisway, the voltage Vw=V1−V2 is applied between the first and the secondconductive layers included in the memory cell 21. By selecting thepotential Vw appropriately, the organic compound layer 29 providedbetween the conductive layers is physically or electrically changed tocarry out writing of the data “1”. Specifically, at an operating voltagefor reading, the electrical resistance between the first and secondconductive layers in the state of the data “1” is preferably changed sothat the electrical resistance is much smaller as compared with in thestate of the data “0”. For example, V1 and V2 may be selected from therange of (V1, V2)=(0 V, 5 to 15 V) or (3 to 5 V, −12 to −2 V). Thevoltage Vw may be 5 to 15 V, or −5 to −15 V. It is to be noted that thedistance between the pair of electrodes provided to sandwich the organiccompound layer can be changed in this case.

It is to be noted that a non-selected word line and a non-selected bitline are controlled so that data “1” is not written in the memory cellconnected to the non-selected word line and the non-selected bit line.For example, the non-selected word line and the non-selected bit linemay be made floating. It is necessary to have a characteristic that iscapable of ensuring selectivity, such as a diode characteristic, betweenfirst and second conductive layers constituting a memory cell.

On the other hand, in the case of writing data “0” in the memory cell21, all that is required is that electric action is not applied to thememory cell 21. In circuit operation, for example, in the same way as inthe case of writing data “1”, the memory cell 21 is selected by thedecoders 23 and 24 and the selector 25. However, the output potentialfrom the read/write circuit 26 to the bit line B3 is made nearly equalto the potential of the selected word line W3 or the potential of anon-selected word line so that a voltage (for example, −5 to 5 V) isapplied between the first and second conductive layers constituting thememory cell 21 to such a degree that the electronic property of thememory cell 21 is not changed.

Next, a case of carrying out writing of data by optical action will bedescribed. In the case of carrying out writing of data by opticalaction, the organic compound layer 29 is irradiated with laser lightfrom the light-transmitting conductive layer side (the second conductivelayer 28 here). Here, the organic compound layer 29 included in anorganic memory element in a desired portion is selectively irradiatedwith laser light to destroy the organic compound layer 29. Since thedestroyed organic compound layer is insulated, the electric resistanceof the destroyed organic compound layer is larger when the organicmemory element including the broken organic compound layer is comparedwith another organic memory element. In this way, the change in theelectric resistance between the conductive layers provided with organiccompound layer 29 sandwiched therebetween, by laser irradiation, is usedto carry out writing of data. For example, in the case where an organicmemory element including an organic compound layer that is notirradiated with laser light is made to have data “0”, when data “1” iswritten, an organic compound layer included in an organic memory elementin a desired portion is selectively irradiated with laser light and thusdestroyed to increase the electric resistance.

In addition, in the case of using a conjugated polymer doped with acompound (photoacid generator) that generates acid by absorbing light,when laser irradiation is performed, only an organic memory elementincluding an organic compound layer irradiated with laser light has anelectric conductivity increased. On the other hand, an organic memoryelement including an organic compound layer that is not irradiated withlaser light has no electric conductivity. Therefore, an organic compoundlayer included in an organic memory element in a desired portion isselectively irradiated with laser light to change the electricresistance of the organic memory element including the organic compoundlayer irradiated with laser light, which is used to carry out writing ofdata. For example, in the case where an organic memory element includingan organic compound layer that is not irradiated with laser light ismade to have data “0”, when data “1” is written, an organic compoundlayer included in an organic memory element in a desired portion isselectively irradiated with laser light to increase the electricconductivity.

In the case of laser light irradiation, the change in the electricresistance of an organic memory element depends on the size of thememory cell 21. However, the change is achieved by irradiation withlaser light focused in a range from a few μm to a few hundred μm indiameter. For example, when a laser beam 1 μm in diameter passes at alinear velocity of 10 m/sec, the time for which an organic memoryelement included in one memory cell 21 is irradiated with laser light is100 nsec. In order to change the phase within the short time of 100nsec, the laser power and the power density is preferably 10 mW and 10kW/mm², respectively. In addition, it is preferable to use apulsed-oscillation laser irradiation system when laser light irradiationis selectively performed.

Now, an example of laser irradiation systems will be briefly describedwith reference to FIG. 12. A laser irradiation system 1001 has acomputer 1002 that executes various controls (hereinafter, referred toas a PC 1002), a laser oscillator 1003 that outputs laser light, a powersupply 1004 for the laser oscillator, an optical system 1005 (an NDfilter) for attenuating laser light, an acousto-optic modulator 1006(AOM) for modulating the intensity of laser light, an optical system1007 for reducing a cross section of laser light, which includes a lensand a mirror for changing a light path, a moving mechanism 1009including an X-axis stage and a Y-axis stage, a D/A converter 1010 thatperforms digital-analog conversion of control data output from the PC1002, a driver 1011 that controls the acousto-optic modulator 1006 inaccordance with an analog voltage output from the D/A converter 1010, adriver 1012 that outputs a driving signal for driving the movingmechanism 1009, and an autofocus mechanism 1013 for focusing laser lighton an object to be irradiated (FIG. 12).

As the laser oscillator 1003, a laser oscillator that is capable ofemitting ultraviolet, visible light, or an infrared light can be used.As the laser oscillator, an excimer laser oscillator using KrF, ArF,XeCl, Xe, or the like, a gas laser oscillator using He, He—Cd, Ar,He—Ne, HF, or the like, a solid laser oscillator using a crystal (YAG,GdVO₄, YVO₄, YLF, YAlO₃, or the like) doped with Cr, Nd, Er, Ho, Ce, Co,Ti, or Tm, and a semiconductor laser oscillator using GaN, GaAs, GaAlAs,InGaAsP, or the like can be used. It is to be noted that it ispreferable to apply one of a fundamental wave and the second to fifthharmonics in the case of the solid laser oscillator.

Next, an irradiation method using the laser irradiation system will bedescribed. When the substrate 30 provided with the organic compoundlayer 29 is loaded on the moving mechanism 1009, the PC 1002 detects theposition of the organic compound layer 29 to be irradiated with laserlight by a CCD camera or the like. Then, based on the detected positiondata, the PC 1002 generates moving data for moving the moving mechanism1009.

After this, while the PC 1002 controls the output light intensity of theacousto-optic modulator 1006 through the driver 1011, laser light outputfrom the laser oscillator 1003 is attenuated by the optical system 1005,and then, the light intensity is controlled by the acousto-opticmodulator 1006 so as to be predetermined light intensity. Further, thelight path and the beam-spot shape of the laser light output from theacousto-optic modulator 1006 are changed by the optical system 1007, thelaser light is condensed with a lens, and then, the organic compoundlayer 29 over the substrate 30 is irradiated with the laser lightselectively.

At this point, in accordance with the moving data generated by the PC1002, the moving mechanism 1009 is moved in the X direction and the Ydirection. Accordingly, the predetermined position is irradiated withthe laser light, the light energy density of the laser light isconverted into thermal energy, and thus, the organic compound layer 29provided over the substrate 30 can be selectively irradiated with thelaser light. It is to be noted that the laser light may be moved in theX direction and the Y direction by adjusting the optical system 1007although a case of performing laser light irradiation by moving themoving mechanism 1009 is shown here.

As described above, the aspect according to the present invention, inwhich writing of data is preformed by laser light irradiation, makes itpossible to manufacture a large amount of semiconductor devices easily.Therefore, inexpensive semiconductor devices can be provided.

Next, operation in reading of data from an organic memory will bedescribed (refer to FIG. 1B and FIGS. 9A and 9B). Reading of data iscarried out by using an electronic property between first conductivelayers constituting a memory cell, which is different between a memorycell with data “0” and a memory cell with data “1”. For example, amethod for reading by using difference in electric resistance will bedescribed, where the effective electric resistance between first andsecond conductive layers constituting a memory cell with data “0”(hereinafter, simply referred to as the electric resistance of a memorycell) is R0 at a reading voltage, and the electric resistance of amemory cell with data “1” is R1 (R1<<R0) at a reading voltage. As for asread/write circuit, for example, a circuit 26 using a resistive element46 and a differential amplifier 47, which is shown in FIG. 9A, can beconsidered as a structure of a reading portion. The resistive resistance46 has a resistance value Rr (R1<Rr<R0). A transistor 48 may be usedinstead of the resistive element 46, and a clocked inverter 49 can beused instead of the differential amplifier 47 (FIG. 9B). A signal or aninverted signal that is Hi when reading is carried out and is Lo whenreading is not carried out is input to the clocked inverter 49. Ofcourse, the circuit configuration is not limited to FIGS. 9A and 9B.

When reading of data from the memory cell 21 is carried out, first, thememory cell 21 is selected by the decoders 23 and 24 and the selector25. Specifically, by the decoder 24, a predetermined voltage Vy isapplied to the word line Wy connected to the memory cell 21. Further, bythe decoder 23 and the selector 25, the bit line Bx connected to thememory cell 21 is connected to a terminal P of the read/write circuit26. Accordingly, the potential Vp of the terminal P is a valuedetermined by resistance dividing Vy and V0 by the resistive element 46(resistance value: Rr) and the memory cell 21 (resistance value: R0 orR1). Therefore, when the memory cell 21 has data “0”,Vp0=Vy+(V0−Vy)*R0/(R0+Rr). Also, when the memory cell 21 has data “1”,Vp1=Vy+(V0−Vy)*R1/(R1+Rr). Accordingly, by selecting Vref so as to bebetween Vp0 and Vp1 in FIG. 9A or selecting the point of variation ofthe clocked inverter 49 so as to be between Vp0 and Vp1 in FIG. 9B, anoutput potential Vout of Lo/Hi (or Hi/Lo) is output in accordance withdata “0”/“1” so that reading can be carried out.

For example,_assume that the differential amplifier 47 is made tooperate at Vdd=3 V, and Vy, V0, and Vref are 0 V, 3 V, and 1.5 V,respectively. On the condition of R0/Rr=Rr/R1=9, Hi is output as Vout inaccordance with Vp0=2.7 V when a memory cell has data “0”, or Lo isoutput as Vout in accordance with Vp1=0.3 V when a memory cell has data“1”. In this way, reading from a memory cell can be carried out.

According to the method described above, the state of the electricresistance of an organic memory element is read in voltage by usingdifference in resistance value and resistance division. Of course, themethod for reading is not limited to this method. For example, readingmay be carried out by using difference in current value other than usingdifference in electric resistance. In addition, when an electronicproperty a memory cell has different diode characteristics in thresholdvoltage in the case of data “0” and data “1”, reading may be carried outby using difference in threshold voltage.

Embodiment Mode 2

As described above, a semiconductor device has a memory. A semiconductordevice that is different from the semiconductor device in the embodimentmode described above will be described below with reference to theaccompanying drawings.

A memory 216 has a memory cell array 222 in which a memory cell 221 isprovided in a matrix, decoders 223 and 224, a selector 225, and aread/write circuit 226 (FIG. 10). It is to be noted the structure of thememory 216 shown here is just an example, another circuit such as asense amplifier, an output circuit, or a buffer may be included.

The memory cell 221 a first conductive layer connected to a bit line Bx(1≦x≦m), a second conductive layer connected to a word line Wy (1≦y≦n),a transistor 240, and a memory element 241 (hereinafter, also referredto as an organic memory element 241). The memory element 241 has astructure in which an organic compound layer is sandwiched between apair of electrodes. The transistor 240 has a gate electrode connected tothe word line Wy. One of a source electrode and a drain electrode of thetransistor 240 is connected to the bit line Bx while the other isconnected to one of two terminals of the memory element 241. The otherterminal of the memory element 241 is connected to a common electrode(potential: Vcom).

Next, a cross-sectional structure of the memory 216 that has thestructure described above will be described (refer to FIG. 11).

Cross-sectional structures of the transistor 240, the organic memoryelement 241, and a CMOS circuit 248 included in the selector 225 areshown here. The transistor 240 and the CMOS circuit 248 are providedover a substrate 230, and the organic memory element 241 is formed to beelectrically connected the transistor 240.

The organic memory element 241 is formed to have a laminated body of afirst conductive layer 243, an organic compound layer 244, and a secondconductive layer 245, and an insulating layer 249 is provided theadjacent organic memory elements 241. The insulating layer 249 is formedas a partition for separating the plurality of organic memory elements241. In addition, a source or drain region of the transistor 240 and thefirst conductive layer 243 included in the organic memory element 241are electrically connected to each other.

In addition, each of the first conductive layer 243 and the secondconductive layer 245 is formed with the used of a conductive materialsuch as aluminum (Al), copper (Cu), silver (Ag), or titanium (Ti).

When writing of data is carried out by optical action, one or both ofthe first and second conductive layers 243 and 245 are formed with theused of a light-transmitting material such as indium tin oxide (ITO) orformed to have a thickness through which light is transmitted. Whenwriting of data is carried out by electric action, materials to be usedfor the first conductive layer 243 and the second conductive layer 245are not particularly restricted.

The organic compound layer 244 is formed as described in Embodiment Mode1, for which a single layer or a laminated structure including any ofthe materials mentioned above can be used.

When an organic compound material is used for the organic compound layer244, writing of data is carried out by applying optical action such aslaser light or electric action. In addition, when a conjugated polymerdoped with a photoacid generator is used, writing of data is carried outby optical action. Reading of data does not depend on the material ofthe organic compound layer 244, and is carried out by electric action inany case.

Next, operation in writing of data into the memory 216 will be described(FIGS. 10A to 10C and FIG. 11).

First, operation in writing of data by electric action will be described(refer to FIG. 1B). It is to be noted that the writing is carried out bychanging an electronic property of the memory cell, where the initialstate (a state without electric action applied) of the memory cell isdata “0”, and a state with the electronic property changed is data “1”.

A case of writing data into the memory cell 221 at the n-th row and them-th column will be described here. In the case of writing data “1” inthe memory cell 221, the memory cell 221 is first selected by thedecoders 223 and 224 and the selector 225. Specifically, a predeterminedvoltage V22 is applied to the word line Wn connected to the memory cell221 by the decoder 224. Further, the bit line Bm connected to the memorycell 221 is connected to the read/write circuit 226 by the decoder 223and the selector 225. Then, a write voltage V21 is output from theread/write circuit 226 to the bit line Bm.

In this way, the transistor 240 constituting the memory cell 221 is madein an ON state, and the common electrode and the bit line Bm are thuselectrically connected to the memory element 241 so that a voltage ofapproximately Vw=Vcom−V21 is applied to the memory element 241. Byselecting the potential Vw appropriately, the organic compound layer 244provided between the conductive layers is physically or electricallychanged to carry out writing of the data “1”. Specifically, at anoperating voltage for reading, the electrical resistance between thefirst and second conductive layers in the state of the data “1” ispreferably changed so that the electrical resistance is much smaller ascompared with in the state of the data “0”, and the memory element 241may be simply short circuited. It is to be noted that the potentialsV21, V22, and Vcom may be selected from the range of (V21, V22, Vcom)=(5to 15 V, 5 to 15 V, 0) or (−12 to 0 V, −12 to 0 V, 3 to 5 V). Thevoltage Vw may be 5 to 15 V, or −5 to −15 V. It is to be noted that thedistance between the pair of electrodes provided to sandwich the organiccompound layer can be changed in this case.

It is to be noted that a non-selected word line and a non-selected bitline are controlled so that data “1” is not written in the memory cellconnected to the non-selected word line and the non-selected bit line.Specifically, while a voltage (for example, 0 V) that puts a transistorin the connected memory cell connected into an OFF state is applied tothe non-selected word line, the non-selected bit line may be madefloating, or a potential that is nearly equal to Vcom may be applied tothe non-selected bit line.

On the other hand, in the case of writing data “0” in the memory cell221, all that is required is that electric action is not applied to thememory cell 221. In circuit operation, for example, in the same way asin the case of writing data “1”, the memory cell 221 is selected by thedecoders 223 and 224 and the selector 225. However, the output potentialfrom the read/write circuit 226 to the bit line Bm is made nearly equalto Vcom, or the bit line Bm is made floating. Consequently, a smallvoltage (for example, −5 to 5 V) or no voltage is applied to the memoryelement 241, and thus, the electric property is not changed so thatwriting of data “0” is achieved.

Next, a case of carrying out writing of data by optical action will bedescribed. In this case, the organic compound layer 244 included in theorganic memory element 241 is irradiated with laser light from thelight-transmitting conductive layer side (the second conductive layer245 here).

When an organic compound material is used for the organic compound layer244, the organic compound layer 244 is oxidized or carbonized by laserlight irradiation to be insulated. Thus, the resistance value of theorganic memory element 241 irradiated with laser light is increasedwhile the resistance value of the organic memory element 241 that is notirradiated with laser light is not changed. In addition, when aconjugated polymer doped with a photoacid generator is used, an electricconductivity is given to the organic compound layer 244 by laser lightirradiation. Namely, an electric conductivity is given to the organicmemory element 241 irradiated with laser light while no electricconductivity is given to the organic memory element 241 that is notirradiated with laser light.

Next, operation in reading of data by electric action will be described.Reading of data is carried out by using an electronic property of thememory element 241, which is different between a memory cell with data“0” and a memory cell with data “1”. For example, a method for readingby using difference in electric resistance will be described, where theelectric resistance of a memory element constituting a memory cell withdata “0” is R0 at a reading voltage, and the electric resistance of amemory cell constituting a memory cell with data “1” is R1 (R1<<R0) at areading voltage. As for as read/write circuit, for example, a circuit226 using a resistive element 246 and a differential amplifier 247,which is shown in FIG. 10B, can be considered as a structure of areading portion. The resistive element 246 has a resistance value Rr(R1<Rr<R0). A transistor 250 may be used instead of the resistiveelement 246, and a clocked inverter 251 can be used instead of thedifferential amplifier 247 (FIG. 10C). Of course, the circuitconfiguration is not limited to FIGS. 10B and 10C.

When reading of data from the memory cell 221 at the n-th row and them-th column is carried out, first, the memory cell 221 is selected bythe decoders 223 and 224 and the selector 225. Specifically, by thedecoder 224, a predetermined voltage V24 is applied to the word line Wnconnected to the memory cell 221 to put the transistor 240 into an ONstate. Further, by the decoder 223 and the selector 225, the bit line Bxconnected to the memory cell 221 is connected to a terminal P of theread/write circuit 226. Accordingly, the potential Vp of the terminal Pis a value determined by resistance dividing Vcom and V0 by theresistive element 246 (resistance value: Rr) and the memory element 241(resistance value: R0 or R1). Therefore, when the memory cell 221 hasdata “0”, Vp0=Vcom+(V0−Vcom)*R0/(R0+Rr). Also, when the memory cell 221has data “1”, Vp1=Vcom+(V0−Vcom)*R1/(R1+Rr). Accordingly, by selectingVref so as to be between Vp0 and Vp1 in FIG. 10B or selecting the pointof variation of the clocked inverter 251 so as to be between Vp0 and Vp1in FIG. 10C, an output potential Vout of Lo/Hi (or Hi/Lo) is output inaccordance with data “0”/“1” so that reading can be carried out.

For example, assume that the differential amplifier 47 is made tooperate at Vdd=3 V, and Vcom, V0, and Vref are 0 V, 3 V, and 1.5 V,respectively. On the condition of R0/Rr=Rr/R1=9 and the condition thatthe ON resistance of the transistor 240 is negligible, Hi is output asVout in accordance with Vp0=2.7 V when a memory cell has data “0”, or Lois output as Vout in accordance with Vp1=0.3 V when a memory cell hasdata “1”. In this way, reading from a memory cell can be carried out.

According to the method described above, the state of the electricresistance of the memory element 241 is read in voltage by usingdifference in the resistance value of the memory element 241 andresistance division. Of course, the method for reading is not limited tothis method. For example, reading may be carried out by using differencein current value other than using difference in electric resistance. Inaddition, when an electronic property of a memory cell has differentdiode characteristics in threshold voltage in the case of data “0” anddata “1”, reading may be carried out by using difference in thresholdvoltage.

It is to be noted that the present embodiment mode can be carried outfreely in combination with the embodiment mode described above.

Embodiment Mode 3

Writing of data in an organic memory included in a semiconductor device20 according to the present invention is carried out by optical orelectrical action. When writing of data is carried out by opticalaction, a plurality of semiconductor devices 20 are formed over aflexible substrate 31 and then irradiated with laser light by a laserlight irradiating means 32 so that writing of data can be continuouslycarried out easily. Moreover, when this manufacturing process isemployed, the semiconductor devices 20 can be easily manufactured inlarge quantity (FIG. 3A). Accordingly, the inexpensive semiconductordevices 20 can be provided.

In addition, an organic compound layer included in an organic memoryelement can be intentionally dissolved or destroyed by heating to themelting point or more. Namely, writing of data can be carried out alsoby heat treatment as long as different heating temperatures are used.Accordingly, a manufacturing process using different heatingtemperatures may also be employed. For example, the flexible substrate31 with a plurality of semiconductor devices formed is made to be a roll51 (FIG. 3B). Then, writing of data may be carry out in such a way thatdifferent temperatures are used in heat treatment by a heating means 52.The heating means 52 is controlled by a control means 53.

It is to be noted that the present embodiment mode can be carried outfreely in combination with the embodiment modes described above.

Embodiment Mode 4

As an example of applications of a semiconductor device according to thepresent invention, there is a feature that non-contact writing andreading of data are possible since the organic memory element isprovided. The data transmission methods are classified broadly intothree of an electromagnetic coupling method of communicating by mutualinduction with a pair of coils disposed in the opposed position, anelectromagnetic induction method of communicating by an inductiveelectromagnetic field, and an electric wave method of communicating byusing electric waves, and any of these methods may be employed. Anantenna 18 that is used for transmitting data can be provided in twoways. One way is to provide the antenna 18 over a substrate 36 overwhich a plurality of elements including an organic memory element andthe like are formed (FIGS. 4A and 4C), and the other way is to providethe antenna 18 so as to be connected to a terminal portion 37 that isprovided on a substrate 36 over which a plurality of elements includingan organic memory element are formed (FIGS. 4B and 4D). The plurality ofelements provided over the substrate 36 is referred to as a group ofelements 35 here.

In the case of the former structure (FIGS. 4A and 4C), the group ofelements 35 and a conductive layer that functions as the antenna 18 areprovided over the substrate 36. In the shown structure, the conductivelayer that functions as the antenna 18 is provided in the same layer asthe second conductive layer 28. However, the present invention is notrestricted to the structure described above, and the antenna 18 may beprovided in the same layer as the first conductive layer 27.Alternatively, an insulating film may be provided so as to cover thegroup of elements 35, and the antenna 18 may be provided over theinsulating film.

In the latter structure (FIGS. 4B and 4D), the group of elements 35 andthe terminal portion 37 are provided over the substrate 36. In the shownstructure, a conductive layer provided in the same layer as the secondconductive layer 28 is used as the terminal portion 37. Then, asubstrate 38 over which the antenna 18 is provided is attached so as tobe connected to the terminal portion 37. A conductive particle 39 and aresin 40 are provided between the substrate 36 and the substrate 38.Note that a conductive layer which functions as the antenna 18 isconnected to a transistor constituting a wave-shaping circuit or arectification circuit provided in the group of elements 35. After datais rectified in the wave-shaping circuit or the rectification circuit,data sent from the outside without contact is sent to the organic memoryelement and writing or reading data is carried out through a writingcircuit or a reading circuit

The group of elements 35 can be provided inexpensively by forming andthen dividing a plurality of groups of elements over a large areasubstrate. The substrate to be used in this case can be a glasssubstrate, a flexible substrate, and the like.

A plurality of transistors and organic memory elements included in thegroup of elements 35, and the like may be provided over a plurality oflayers, that is, may be formed by using a plurality of layers. When thegroup of elements 35 is formed over a plurality of layers, an interlayerinsulating film is used. For the interlayer insulating film, a resinmaterial such as an epoxy resin and an acryl resin, a resin materialsuch as a light-transmitting polyimide resin, a compound materialincluding a siloxane material such as a siloxane resin, a materialcontaining a water-soluble homopolymer and a water-soluble copolymer,and an inorganic material are preferably used. The siloxane materialcorresponds to a material including a Si—O—Si bond. Siloxane has a framestructure formed by bonding between silicon (Si) and oxygen (O), wherean organic group including at least hydrogen (for example, an alkylgroup and aromatic hydrocarbon) as a substituent. However, a fluorogroup may be used as a substituent, or an organic group including atleast hydrogen and a fluoro group may be used as substituents.

For the interlayer insulating film, a material with low dielectricconstant is preferably used for decreasing parasitic capacitance that isgenerated between the layers. When the parasitic capacitance isdecreased, high-speed operation as well as low power consumption can beachieved.

The plurality of transistors included in the group of elements 35 mayuse any of an amorphous semiconductor, a microcrystalline semiconductor,a polycrystalline semiconductor, an organic semiconductor, and the likefor active layers. However, it is preferable to use an active layercrystallized by using a metal element as a catalyst or an active layercrystallized by laser irradiation in order to obtain a transistor thathas favorable characteristics. Further, it is preferable to use, as anactive layer, a semiconductor layer formed by plasma CVD with the use ofa SiH₄/F₂ gas or a SiH₄/H₂ gas (Ar gas) or a semiconductor layerobtained by irradiating semiconductor layer with laser.

The plurality of transistors included in the group pf elements 35 canuse a crystalline semiconductor layer (a low temperature polysiliconlayer) crystallized at a temperature of 200 to 600° C. (preferably 350to 500° C.) or a crystalline semiconductor layer (a high temperaturepolysilicon layer) crystallized at a temperature of 600° C. or higher.When a high temperature polysilicon layer is formed over a substrate, aquartz substrate is preferably used since a glass substrate is weak toheat.

It is preferable that the active layers (in particular, channel regions)of the transistors included in the group of elements 35 be doped with ahydrogen or halogen element at a concentration of 1×10¹⁹ to 1×10²²atoms/cm³; preferably at a concentration of 1×10¹⁹ to 5×10²⁰ atoms/cm³.Then, an active layer in which a crack is not easily generated with fewdefects can be obtained.

Further, it is preferable to provide a barrier film that blockscontaminants such as an alkaline metal so as to wrap the transistorsincluded in the group of elements 35 or the group of elements 35 itself.Then, the group of elements 35, which is not contaminated and hasreliability improved, can be provided. It is to be noted that a siliconnitride film, a silicon nitride oxide film, a silicon oxynitride film orthe like can be used for the barrier film.

Further, the thicknesses of the active layers of the transistorsincluded in the group of elements 35 is preferably 20 to 200 nm,preferably 40 to 170 nm, more preferably 45 to 55 nm and 145 to 155 nm,and even more preferably 50 nm and 150 nm. Then, the group of elements35, in which a crack is not easily generated even in the case of beingbent, can be provided.

Further, it is preferable that crystals for forming the active layers ofthe transistors included in the group of elements 35 be formed so as toinclude a crystal boundary extending in parallel to a carrier flowdirection (a channel length direction). This active layer is formedpreferably by using a continuous oscillation laser, or a pulsed laserthat operates at a frequency of 10 MHz or higher, preferably 60 to 100MHz.

Further, it is preferable that the transistors included in the group ofelements 35 have an S value (a sub-threshold value) of 0.35 V/dec orless (preferably 0.09 to 0.25 V/dec, and a mobility of 10 cm²/Vs ormore. These characteristics can be achieved when the active layers areformed by using a continuous oscillation laser or a pulsed laser thatoperates at a frequency of 10 MHz or higher.

Further, the group of elements 35 has characteristics of 1 MHz orhigher, preferably 10 MHz or higher (at 3 to 5 V), measured by a ringoscillator, or has a frequency characteristic per gate, 100 kHz orhigher, preferably 1 MHz or higher (at 3 to 5V).

The antenna 18 is preferably formed by a droplet discharging method withthe use of a conductive paste containing nanoparticles of gold, silver,copper, or the like. The droplet discharging method is a generic termfor a method of forming a pattern by discharging droplets, such as anink-jet method and a dispenser method, and has various advantages suchthat a material can be used more efficiently.

The structure described above makes it possible to manufacture an RFIDthat has a quite small area (1 cm×1 cm).

Further, in the semiconductor device shown in the present embodimentmode, an integrated circuit that is formed by using an IC chip may bemounted on the group of elements 35. By mounting an integrated circuitthat is formed by using an IC chip, the write voltage of a memoryelement can be controlled to be 14 V or more. Further, since the area ofa write circuit, a read circuit, and the like of a memory element can bereduced, the size (area) of an RFID on which all of these circuits aremounted can be made smaller than 1 cm square (1 cm×1 cm).

Although a substrate 42 on which a group of elements 35 is provided maybe used as it is, the group of elements 35 over the substrate 42 may bepeeled off (FIG. 5A) and attached to a flexible substrate 43 (FIG. 5B)in order to create added value.

The group of elements 35 can be peeled off from the substrate 42 by (1)a method of providing a metal oxide film between the substrate 42 ofhigh heat resistance and the group of elements 35 and weakening themetal oxide film by crystallization, (2) a method of providing anamorphous silicon film containing hydrogen between the substrate 42 ofhigh heat resistance and the group of elements 35 and removing theamorphous silicon film by laser light irradiation or etching, or (3) amethod of removing the substrate 42 of high heat resistance, over whichthe group of elements 35 is formed, mechanically or by etching with asolution or a gas such as ClF₃.

In addition to the methods described above, by providing a metal layer(for example, tungsten (W), molybdenum (Mo), titanium (Ti), tantalum(Ta), or cobalt (Co)), a metal oxide film (for example, tungsten oxide(WOx), molybdenum oxide (MoOx), titanium oxide (TiOx), tantalum oxide(TaOx), or cobalt oxide (CoOx)), or a laminated structure of a metalfilm and a metal oxide film (for example, W and WOx, Mo and MoOx, Ti andTiOx, or Co and CoOx) that serves as a peeling layer between thesubstrate 42 and the group of elements 35, the substrate 42 and thegroup of elements 35 can be separated from each other by a physicalforce. For example, in the case of FIG. 11, a group of elements such asthe transistor 240, the CMOS circuit 248, and the organic memory element241 is provided over the substrate 230 with this peeling layerinterposed therebetween, and then peeled off from the substrate 230. Itis to be noted that the peeling physically is made easier by, before thepeeling, selectively irradiating a portion except the transistor 240,the CMOS circuit 248, and the organic memory element 241 with laserlight to expose the peeling layer. In addition, it is also possible topeel off the group of elements physically from the substrate afterselectively forming an opening to expose the peeling layer and thenremoving a portion of the peeling layer with an etching agent such ashalogen fluoride (for example, ClF₃).

In addition, the peeled group of elements 35 may be attached to theflexible substrate 43 with the use of a commercial adhesive such as anepoxy resin adhesive and an adhesive using a resin additive.

As described above, a semiconductor device that is thin, lightweight,and is not easily broken even in the case of being dropped can beprovided by attaching the group of elements 35 to the substrate 43.Also, since the flexible substrate 43 has flexibility, the semiconductordevice can be attached onto a curved or odd-shaped surface so thatvarious applications are realized. For example, a wireless tag that isone mode of the semiconductor device 20 according to the presentinvention can be closely attached to a curved surface such as a medicinebottle (FIGS. 5C and 5D). Moreover, an inexpensive semiconductor devicecan be provided when the substrate 42 is reused.

It is to be noted that the present embodiment mode can be carried outfreely in combination with the embodiment modes described above.

Embodiment Mode 5

In the present embodiment, a case of forming a flexible semiconductordevice by a peeling process will be described (FIG. 6A). A semiconductordevice includes a flexible protective layer 2301, a flexible protectivelayer 2303 including an antenna 2304, and a group of elements 2302formed by a peeling process. The antenna 2304 formed over the protectivelayer 2303 is electrically connected to the group of elements 2302. Inthe shown structure, the antenna 2304 is formed only over the protectivelayer 2303. However, the present invention is not restricted to thisstructure, and the antenna 2304 may be formed also over the protectivelayer 2301. It is to be noted that a barrier film composed of a siliconnitride film is preferably formed between the group of elements 2302 andthe protective layers 2301 and 2303. Then, a semiconductor device inwhich the group of elements 2302 is not contaminated with reliabilityimproved can be provided.

It is preferable that the antenna 2304 be formed by using silver,copper, or a metal plated with them. The group of elements 2302 and theantenna 2304 are connected by performing UV treatment or supersonictreatment with the use of an anisotropic conductive film. However, thepresent invention is not restricted to this method, and various methodscan be employed as well.

It is preferable that the group of elements 2302 sandwiched between theprotective layers 2301 and 2303 be formed so as to have a thickness of 5μm or less, preferably 0.1 to 3 μm (FIG. 6B). When the thickness of thestacked protective layers 2301 and 2303 is d, the thickness of each ofthe protective layers 2301 and 2303 is preferably (d/2)±30 μm, and morepreferably (d/2)±10 μm. Further, it is preferable that the thickness ofeach of the protective layers 2301 and 2303 be 10 to 200 um. Moreover,the group of elements 2302 has an area of 5 mm square (25 mm²) or less,and preferably 0.3 to 4 mm square (0.09 to 16 mm²).

The protective layers 2301 and 2303 are each formed by using an organicresin material, and so, are highly resistant to bending. The group ofelements 2302 itself formed by a peeling process is also highlyresistant to bending as compared with a single crystallinesemiconductor. Further, since the group of elements 2302 and theprotective layers 2301 and 2303 can be closely attached to each otherwithout any space, a completed semiconductor device itself is alsohighly resistant to bending. The group of elements 2302 surrounded bythese protective layers 2301 and 2303 may be disposed on the surface ofor inside another object or implanted in paper.

Now, a case of attaching the group of elements formed by a peelingprocess to a curved substrate will be described (FIG. 6C). In thedrawing, one transistor selected from the group of elements formed by apeeling process is shown. This transistor is formed linearly in acurrent flow direction. Namely, a drain electrode 2305, a gate electrode2307, and a source electrode 2306 are located linearly. Then, thecurrent flow direction and the direction in which the substrate draws anarc are arranged to be perpendicular to each other. With thisarrangement, even when the substrate is bent to draw an arc, theinfluence of stress is small, and variation in characteristics of thetransistors included in the group of elements can be suppressed.

In order to prevent active elements such as a transistor from beingbroken due to stress, it is preferable that the area of active regions(silicon island portion) of the active elements be made to be 1 to 50%(preferably 1 to 30%) with respect to the entire area of the substrate.In a region where there is no active element such as a TFT, a baseinsulating film material, an interlayer insulating film material and awiring material are mainly provided. It is preferable that the areaother than the active regions of a transistor and the like be 60% ormore of the entire area of the substrate. Accordingly, a highlyintegrated semiconductor device that can be easily bent at the same timecan be provided.

It is to be noted that the present embodiment mode can be carried outfreely in combination with the embodiment modes described above.

Embodiment Mode 6

In addition, when an organic memory is integrated in a semiconductordevice according to the present invention, it is preferable to providefeatures as described below.

In order to operate at the operating frequency of a logic circuit in thesemiconductor devices that send and receive data without contact such asa wireless tag (typically, 10 kHz to 1 MHz), it is preferable that theread time be 1 nsec to 100 usec. In the present invention, a read timeof 100 usec or less can be achieved since it is not necessary to changea property of the organic compound in a read operation.

The write time is preferably short as a matter of course. However, it isunlikely that a write operation is often performed, and the permissiblerange of the write time is 100 nsec/bit to 10 msec/bit depending onapplications. For example, in the case of writing 256 bit, a time periodof 2.56 seconds is required at 10 msec/bit. In the present invention, aread time of 10 msec/bit or less can be achieved although it isnecessary to change to a property of the organic compound in a writeoperation and the write operation requires more time than a readoperation. The write time can be reduced by increasing the write voltageor performing parallelization of writing.

It is preferable that the storage capacity of the memory beapproximately 64 bit to 64 Mbit. As a use of the semiconductor devicesuch as the wireless chip, in the case of storing only UID (UniqueIdentifier) and another slight information in the semiconductor deviceand using another file sever for main data, the memory needs only have astorage capacity of approximately 64 bit to 8 kbit. In the case ofstoring data such as history information in the semiconductor device, itis preferable that the storage capacity the memory be larger, and beapproximately 8 kbit to 64 Mbit.

In addition, the communication distance of the semiconductor device suchas the wireless chip is closely related to the power consumption of thesemiconductor device. Commonly, a larger communication distance can beachieved as the power consumption is smaller. In particular, in a readoperation, it is preferable that the power consumption be made 1 mW orless. In a write operation, the communication distance can be allowed tobe short depending on applications, and the power consumption is allowedto be larger than in a read operation, and for example, is preferablymade to be 5 mW or less. In the present invention, the power consumptionof the organic memory in a read operation can achieve 10 uW to 1 mWalthough the power consumption of course depends on the storage capacityand the operating frequency. In a write operation, the power consumptionis increased since a higher voltage is needed than in a read operation.Although the power consumption in a write operation also depends on thestorage capacity and the operating frequency, the power consumption canachieve 50 uW to 5 mW.

It is preferable that the area for a memory cell be small, and an areaof 100 nm square to 30 um square can be achieved. In a passive type inwhich a memory cell has no transistor, the area for the memory cell isdetermined by the width of a wiring, and thus, a small-sized memory cellthat is comparable with the minimum process size can be achieved. Inaddition, in an active type in which a memory cell has one transistor, asmaller area for the memory cell can be achieved as compared with a DRAMincluding a capacity element and an SRAM using a plurality oftransistors although the area is increased for arranging the transistor.The achievement of an area of 30 um square or less for a memory cellmakes it possible to make the area for a memory cell 1 mm square or lessin the case of a 1 kbit memory. Further, the achievement of an area ofapproximately 100 nm square for a memory cell makes it possible to makethe area for a memory cell 1 mm square or less in the case of a 64 Mbitmemory. Accordingly, the area of the semiconductor device can bereduced.

It is to be noted that these features of the organic memory depend oncharacteristics of a memory element. As for the characteristics of amemory element, it is preferable that the voltage required for the caseof electrical writing be low to such a degree that writing is notcarried out in reading, and the voltage is preferably 5 to 15 V, morepreferably 5 to 10 V. Further, it is preferable that the current valuethat flows in the memory element in writing be made to be approximately1 nA to 30 uA. This given value makes it possible to reduce powerconsumption and make a boost circuit smaller to reduce the area of thesemiconductor device. It is preferable that the time required forapplying a voltage to the memory element to change a property of thememory element be made to be 100 nsec to 10 msec in response to thewrite time of the organic memory. It is preferable that the area of thememory element be 100 nm square to 10 um square. This given value makesit possible to achieve a small-sized memory cell and thus reduce thearea of the semiconductor device.

It is to be noted that the present embodiment mode can be carried outfreely in combination with the embodiment modes described above.

Embodiment Mode 7

The application range of the semiconductor device according to thepresent invention is wide. For example, a wireless tag that is one modeof the semiconductor device 20 according to the present invention can beprovided and used for bills, coins, securities, certificates, bearerbonds, containers for wrapping, books, storage mediums, personalbelongings, vehicles, groceries, garments, health products, dailycommodities, medicines, electronic devices, and the like.

The bills and coins are money that circulates in the market, andincludes one that can be used in the same way as money in a specificarea (cash voucher), a commemorative coin, and the like. The securitiesindicate a check, certificate, a promissory note, and the like (FIG.7A). The certificates indicate a license, a resident's card, and thelike (FIG. 7B). The bearer bonds indicate a stamp, a rice coupon,various gift coupons, and the like (FIG. 7C). The containers forwrapping indicate a wrapper for a packed lunch and the like, a plasticbottle, and the like (FIG. 7D). The books indicates a magazine, adictionary, and the like (FIG. 7E). The storage mediums indicate a DVDsoftware, a video tape, and the like (FIG. 7F). The vehicles indicate awheeled vehicle such as a bicycle, a ship, and the like (FIG. 7G). Thepersonal belongings indicate to a bag, glasses, and the like, (FIG. 7H).The groceries indicate foods, beverages, and the like. The garmentsindicate clothes, shoes, and the like. The health products indicate amedical apparatus, a health appliance, and the like. The dailycommodities indicate furniture, lighting apparatus, and the like. Themedicines indicate a drug, an agricultural chemical, and the like. Theelectronic devices indicate a liquid crystal display device, an ELdisplay device, television sets (a television receiver and a thintelevision receiver), a cellular phone, and the like.

By providing wireless tags for bills, coins, securities, certificates,bearer bonds, and the like, falsification can be prevented. In addition,by providing wireless tags for containers for wrapping, books, storagemediums, personal belongings, groceries, daily commodities, electronicdevices, and the like, an inspection system and a system of a rentalstore, and the like can be facilitated. By providing wireless tags forvehicles, health products, medicines, and the like, falsification andtheft can be prevented, and an error in taking a drug can be preventedin the case of the medicines. The wireless tag can be provided by beingattached to the surface of an article or being implanted in an article.For example, the wireless tag can be implanted in paper in the case of abook, and can be implanted in an organic resin in the case of a packagecomposed of the organic resin.

As described above, highly functional systems can be obtained byapplying wireless tags to management of articles and a distributionsystem. For example, there is a case where a reader/writer 95 isprovided on a side of a portable terminal including a display portion94, and a wireless tag 96 that is one mode of the semiconductor deviceaccording to the present invention is provided on a side of a product 97(FIG. 8A). In this case, when the wireless tag 96 is held over thereader/writer 95, data of the product 97 such as a primary material, acountry of origin, and a history of distribution are displayed on thedisplay portion 94. Further, as another example, there is a case where areader/writer 95 is provided beside a conveyor belt (FIG. 8B). In thiscase, inspection of the product 97 can be easily performed.

It is to be noted that the present embodiment mode can be carried outfreely in combination with the embodiment modes described above.

Embodiment 1

In the present embodiment, a result of writing data by electric actionto an organic memory element manufactured over a substrate will bedescribed.

The organic memory element is an element for which a first conductivelayer, a first organic compound layer, a second organic compound layer,and a second conductive layer are sequentially stacked over a substrate.The first conductive layer, the first organic compound layer, the secondorganic compound layer, and the second conductive layer are formed byusing a compound of silicon oxide and indium tin oxide,4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (may be abbreviatedas TPD), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (may beabbreviated as α-NPD), and aluminum, respectively. The first organiccompound layer and the second organic compound layer are formed so as tohave a film thickness of 10 nm and 50 nm, respectively. The size of theelement is 2 mm×2 mm.

First, the results of measuring current-voltage characteristics of theorganic compound element before and after writing data by electricaction will be described with reference to FIG. 13.

In FIG. 13, the horizontal axis indicates a voltage value, the verticalaxis indicates a current value, plots 261 show current-voltagecharacteristics of the organic memory element before writing data byelectric action, and plots 262 show current-voltage characteristics ofthe organic memory element after writing data by electric action. Theelectric action is performed by increasing voltage gradually from 0V. Asshown by the plots 261, the current value increases gradually as thevoltage is increased, and it is determined that the current valuedrastically increases approximately at 20 V. Namely, this drasticincrease shows that writing in this element can be carried out at 20 V.Therefore, the curve in the range of 20 V or less, the plots 261, showscurrent-voltage characteristics of a memory cell into which writing isnot carried out, and the plots 262 show current-voltage characteristicsof the memory cell into which writing is carried out.

Further, FIG. 13 shows a substantial change in the current-voltagecharacteristics of the organic memory element before and after writingdata. For example, at an applied voltage of 1 V, the current valuebefore writing data is 4.8×10⁻⁵ mA while the current value after writingdata is 1.1×10² mA. Accordingly, writing data results in a seven-digitchange in the current value.

As described above, the resistance value of the organic memory elementis changed after writing data, and the organic memory element can serveas a memory circuit when the change in the resistance value of thisorganic memory element is read in voltage or current.

Further, in the case of using the organic memory element described aboveas a memory circuit, a predetermined voltage value (a voltage value thatis enough to keep from short-circuiting) is applied to the organicmemory element each time a data reading operation is performed, andreading of the resistance value is carried out. Therefore, thecurrent-voltage characteristics of the organic memory element arerequired to be characteristics that are not changed even when a readingoperation is repeatedly conducted, that is, even when a predeterminedvoltage value is repeatedly applied.

Now, the result of measuring current-voltage characteristics of anorganic memory element after reading data will be described withreference to FIG. 14.

In this experiment, current-voltage characteristics of the organicmemory element are measured each time a data reading operation isperformed once. Since the data reading operation is performed five timesin total, the current-voltage characteristics of the organic memoryelement are measured five times in total. This measurement ofcurrent-voltage characteristics is conducted on two organic memoryelements of an organic memory element that has a resistance valuechanged by carrying out writing of data by electric action and anorganic memory element that has an unchanged resistance value.

In FIG. 14, the horizontal axis indicates a voltage value, the verticalaxis indicates a current value, plots 271 show current-voltagecharacteristics of the organic memory element that has the resistancevalue changed by carrying out writing of data by electric action, andplots 272 show current-voltage characteristics of the organic memoryelement that has the unchanged resistance value.

As will be appreciated from the plots 271, the current-voltagecharacteristics of the organic memory element before writing showespecially favorable repeatability at a voltage value of 1 V or more.Similarly, as will be appreciated from the plots 272, thecurrent-voltage characteristics of the organic memory element that hasthe resistance value changed by carrying out writing of data showespecially favorable repeatability at a voltage value of 1 V or more.

From the results described above, the current-voltage characteristicsare not changed even when a data reading operation is repeatedlyconducted more than once. Accordingly, the organic memory elementdescribed above can be used as a memory circuit.

Embodiment 2

In the present embodiment, a semiconductor device according to theembodiment mode described above will be described with reference toFIGS. 16A and 16B. FIG. 16 A is a photograph of a semiconductor device6001 observed with an optical microscope, and FIG. 16B is a patterndiagram of FIG. 16A.

As shown in FIG. 16B, a memory cell array 6002 in which memory cells arearranged in a matrix, a portion of a column decoder 6003, a portion of arow decoder 6004, selectors 6007 and 6008, and a read/write circuit 6005in the semiconductor device 6001 are observed. Further, a dashed line6009 shown in FIG. 16B indicates a second conductive layer of an organicmemory element.

FIG. 17 shows a write characteristic of the semiconductor device shownin FIGS. 16A and 16B, where the size of a memory cell in a horizontalplane is 5 μm×5 μm, and the write time is 100 ms. It is to be noted thatwriting is carried out here in such a way that a voltage is applied toan organic memory element to short-circuit the organic memory element.As for the structure of the organic memory element, a first electrode,an organic compound layer, and the second conductive layer are formed byusing titanium, a-NPD, and aluminum, respectively. Writing of data iscarried out by applying a pulse voltage to this organic memory elementfor 100 ms. It is to be noted that the organic memory element hereincludes a thin film transistor and a memory element.

In FIG. 17, the horizontal axis indicates a pulse voltage, and thevertical axis indicates a rate of successful writing at the pulsevoltage or less (success rate). Writing is started when the writevoltage is 5 V, and writing can be carried out in 6 (9.38%) out of 64memory cells. Although the 64 memory cells are used here, the number ofmemory cells is not limited to 64. For example, only one memory cell canserve as a memory. Further, writing can be carried out in 33 (52%) ofthe 64 memory cells in the semiconductor device when the write voltageis 6 V, writing can be carried out in 45 (70%) of the 64 memory cells inthe semiconductor device when the write voltage is 9 V, writing can becarried out in 60 (93%) of the 64 memory cells in the semiconductordevice when the write voltage is 11 V, and the 64 memory cells (100%) inthe semiconductor device are successful in writing when the writevoltage is 14 V.

It is to be noted that writing is possible also when the write time inthis case is 10 to 100 ms. Further, writing is also possible for a shorttime of 10 ms or less depending on the structure of the memory cells.

From the result described above, writing into the memory cells shown inthe present embodiment is possible at a write voltage of 5 to 14 V.

Embodiment 3

In the present embodiment, current-voltage characteristics obtained whenwriting of data is carried out electrically in an organic memory elementmanufactured over a substrate will be described with reference to FIGS.18A and 18B. It is to be noted that writing is carried out here in sucha way that a voltage is applied to an organic memory element toshort-circuit the organic memory element. In addition, in each of FIGS.18A and 18B, the horizontal axis indicates a voltage that is applied tothe organic memory element, and the vertical axis indicates a currentvalue that flows in the organic memory element.

The organic memory element here is formed in such away that a firstconductive layer is formed on a glass substrate by sputtering, anorganic compound layer is formed on the first conductive layer byevaporation, and a second conductive layer is formed on the organiccompound layer by evaporation. The size of the organic memory elementformed here in the horizontal plane is 20 μm×20 mm.

FIG. 18A shows current-voltage characteristics of an organic memoryelement, where the first conductive layer, the organic compound layer,the second conductive layer are formed by using titanium, a-NPD, andaluminum. It is to be noted that the first conductive layer, the organiccompound layer, the second conductive layer are respectively 100 nm, 10nm, and 200 nm in thickness.

FIG. 18B shows current-voltage characteristics of an organic memoryelement, where the first conductive layer, the organic compound layer,the second conductive layer are formed by using ITO containing siliconoxide, a-NPD, and aluminum. It is to be noted that the first conductivelayer, the organic compound layer, the second conductive layer arerespectively 110 nm, 10 nm, and 200 nm in thickness.

In FIG. 18A, plots 6011 show current-voltage characteristics of theorganic memory element before writing data, and plots 6012 showscurrent-voltage characteristics of the organic memory elementimmediately after writing data, and plots 6013 show current-voltagecharacteristics for the case of applying a voltage the organic memoryelement in which data is written electrically. The write voltage in thiscase 8.29 V, at which the write current is 0.16 mA.

In FIG. 18B, plots 6015 show current-voltage characteristics of theorganic memory element before writing data electrically, and plots 6012shows current-voltage characteristics of the organic memory elementimmediately after writing data, and plots 6013 show current-voltagecharacteristics for the case of applying a voltage the organic memoryelement in which data is written electrically. The write voltage in thiscase 4.6 V, at which the write current is 0.24 mA. As described above,writing into the organic memory element disclosed in the presentinvention is possible at a low voltage, and the current value in thewriting is also small. Therefore, the power consumption for writing intothe organic memory element can be reduced.

When FIGS. 18A and 18B are compared, as shown in FIG. 18A, almost nocurrent flows at less than a certain voltage, in this case, at less than8.29 V in the organic memory element that has the first conductive layerformed by the titanium layer. However, at more than 8.29 V, the currentvalue of the organic memory element drastically changes so that writingof data is carried out, and it is thus determined that writing andreading are easily carried out.

On the contrary, current gradually flows around 4.5 V in the organicmemory element that has the first conductive layer formed by using ITOcontaining silicon oxide. Namely, current flows even before writing. Inaddition, the I-V curve after writing is not linear, and further, theresistance value is larger as compared with the organic memory elementthat has the first conductive layer formed by using titanium afterwriting. Namely, the organic memory element that has the firstconductive layer formed by using ITO containing silicon oxide has asmall difference in resistance value before and after writing, and thus,the memory characteristics can be said to be bad.

In order to provide an element that is excellent in memorycharacteristics, it is preferable that the first conductive layer bemetal layer, typically, a titanium layer.

Embodiment 4

In the present embodiment, the result of observing a cross section of anorganic memory element after writing with a TEM (Transmission ElectronMicroscope) will be described with reference to the accompanyingdrawings. It is to be noted that writing is carried out here in such away that a voltage is applied to an organic memory element toshort-circuit the organic memory element.

First, an organic memory element is formed in such away that a firstconductive layer that is 110 nm in thickness is formed on a glasssubstrate by sputtering, an organic compound layer that is 35 nm inthickness is formed on the first conductive layer by evaporation, and asecond conductive layer that is 270 nm in thickness, is formed on theorganic compound layer by evaporation. The first conductive layer, theorganic compound layer, and the second conductive layer are formed byusing ITO containing silicon oxide, TPD, and aluminum here,respectively. It is to be noted that the size of the organic memoryelement in the horizontal plane is 2 mm×2 mm.

Next, a write voltage is applied to the organic memory element to writedata in the organic memory element, and a cross section of the organicmemory element is observed with a TEM. It is to be noted that a samplefor the TEM is prepared by a process with FIB (Focus Ion beam) to be 0.1μm in width. For the FIB, a Ga ion source is used at 30 kV.

FIG. 19A shows an optical microscope image corresponding to an observedcross-section of the organic memory element after writing data, and FIG.19B and FIGS. 20A and 20B show cross-sectional TEM images correspondingto FIG. 19A. In addition, FIG. 21A shows an optical microscope imagecorresponding to an observed cross-section after writing data, and FIGS.22A and 22B show cross-sectional TEM images corresponding to FIG. 21.Further, for comparison, FIG. 23 shows a cross-sectional TEM image ofthe organic memory element before writing, where the film thickness ofthe film thickness is 34 nm. The magnification in FIG. 19B is ×30000,the magnification in FIGS. 20A and 20B is ×100000, and the magnificationin FIGS. 22A and 22B and FIG. 23 is ×200000.

As shown in FIG. 23, the film thickness of the organic compound layerbefore writing is uniform, and is 34 nm here. FIG. 19B is a TEM image ofPoint (i) in FIG. 19A. As shown in FIG. 19A, a lot of projections areobserved in a portion of the organic memory element aftershort-circuiting the organic memory element. It is FIG. 19B that shows aresult of observing the portion including the projections. The righterportion in FIG. 19B corresponds to a portion near the center of theprojections in FIG. 19A. Namely, it can be said that the projections inthe organic memory element after short circuit are caused by change inthickness of the organic compound layer of the organic memory element.

Further, FIGS. 20A and 20B show observations of the organic memoryelement for the case of multiplying the magnification in FIG. 19B. It isto be noted that FIGS. 20A and 20B show different observed portions. Thefilm thickness of the organic compound layer in the left edge is 90 nmin FIG. 20A while the film thickness of the organic compound layer inthe left edge is 15 nm in FIG. 20B. As described above, in the organiccompound layer of the organic memory element in which data is written,the thickness is partially varied, and it is thus determined that thedistance between the electrodes is changed.

As shown FIG. 20A, it is believed that the projections in the organicmemory element after writing data in FIG. 19A are caused because thefilm thickness of the organic compound layer of the organic memoryelement is changed when the voltage is applied to the organic memoryelement. As shown in FIG. 20A, the film thickness of the organiccompound layer is thinner with being away from the portion including theprojections. FIGS. 22A and 22B show observations of a portion betweenthe projections (refer to Point (ii) in FIG. 21).

As shown in FIGS. 22A and 22B, it is determined that the organic memoryelement is short-circuited after applying the write voltage because theorganic compound layer moves so that the first conductive layer and thesecond conductive layer come contact with each other. Strictly speaking,from the cross-sectional TEM images in FIGS. 22A and 22B, it is can besaid that the film thickness of the organic compound layer is at least 5nm or less at the boundary between the first conductive layer and thesecond conductive layer.

Embodiment 5

In the present embodiment, as for each of samples 1 to 6 as shown inFIGS. 27A to 27F, an organic memory element manufactured over asubstrate, FIGS. 24A to 26B show results of measuring current-voltagecharacteristics when writing of data is carried out electrically intothe organic memory elements. It is to be noted that writing is carriedout here in such a way that a voltage is applied to the organic memoryelement to short-circuit the organic memory element.

In each of FIGS. 24A to 26B, the horizontal axis indicates a voltage,the vertical axis indicates a current density value, circular plots showa result of measuring current-voltage characteristics of the organicmemory element before writing data, and square plots show a result ofmeasuring current-voltage characteristics of the organic memory elementafter writing data. In addition, the size of each of the samples 1 to 6in the horizontal plane is 2 mm×2 mm.

The sample 1 is an element for which a first conductive layer, a firstorganic compound layer, and a second conductive layer are sequentiallystacked. Here, as shown in FIG. 27A, the first conductive layer, thefirst organic compound layer, and the second conducive layer are formedby using ITO containing silicon oxide, TPD and, aluminum, respectively.In addition, the first organic compound layer is formed so as to have athickness of 50 nm. FIG. 24A shows a result of measuring current-voltagecharacteristics of the sample 1.

The sample 2 is an element for which a first conductive layer, a firstorganic compound layer, and a second conductive layer are sequentiallystacked. Here, as shown in FIG. 27B, the first conductive layer, thefirst organic compound layer, and the second conductive layer are formedby using ITO containing silicon oxide, TPD doped with2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (may be abbreviatedas F4-TCNQ), aluminum, respectively. In addition, the first organiccompound layer is formed so as to have a thickness of 50 nm and be dopedwith 0.01 wt % F4-TCNQ. FIG. 24B shows a result of measuringcurrent-voltage characteristics of the sample 2.

The sample 3 is an element for which a first conductive layer, a firstorganic compound layer, a second organic compound layer, and a secondconductive layer are sequentially stacked. Here, as shown in FIG. 27C,the first conductive layer, the first organic compound layer, the secondorganic compound layer, and the second conductive layer are formed byusing ITO containing silicon oxide, TPD, F4-TCNQ, and aluminum,respectively. In addition, the first organic compound layer is formed soas to have a thickness of 50 nm, and the second organic compound layeris formed so as to have a thickness of 1 nm. FIG. 25A shows a result ofmeasuring current-voltage characteristics of the sample 3.

The sample 4 is an element for which a first conductive layer, a firstorganic compound layer, a second organic compound layer, and a secondconductive layer are sequentially stacked. Here, as shown in FIG. 27D,the first conductive layer, the first organic compound layer, the secondorganic compound layer, and the second conductive layer are formed byusing ITO containing silicon oxide, F4-TCNQ, TPD, and aluminum,respectively. In addition, the first organic compound layer is formed soas to have a thickness of 1 nm, and the second organic compound layer isformed so as to have a thickness of 50 nm. FIG. 25B shows a result ofmeasuring current-voltage characteristics of the sample 4.

The sample 5 is an element for which a first conductive layer, a firstorganic compound layer, a second organic compound layer, and a secondconductive layer are sequentially stacked. Here, as shown in FIG. 27E,the first conductive layer, the first organic compound layer, the secondorganic compound layer, and the second conductive layer are formed byusing ITO containing silicon oxide, TPD doped with F4-TCNQ, TPD, andaluminum, respectively. In addition, the first organic compound layer isformed so as to have a thickness of 40 nm and be doped with 0.01 wt %F4-TCNQ, and the second organic compound layer is formed so as to have athickness of 40 nm. FIG. 26A shows a result of measuring current-voltagecharacteristics of the sample 5.

The sample 5 is an element for which a first conductive layer, a firstorganic compound layer, a second organic compound layer, and a secondconductive layer are sequentially stacked. Here, as shown in FIG. 27F,the first conductive layer, the first organic compound layer, the secondorganic compound layer, and the second conductive layer are formed byusing ITO containing silicon oxide, TPD, TPD doped with F4-TCNQ, andaluminum, respectively. In addition, the first organic compound layer isformed so as to have a thickness of 40 nm, and the second organiccompound layer is formed so as to have a thickness of 10 nm and be dopedwith 0.01 wt % F4-TCNQ. FIG. 26B shows a result of measuringcurrent-voltage characteristics of the sample 6.

The experiment results shown in FIGS. 24A to 26B also show substantialchanges in current-voltage characteristics of the organic memoryelements before writing data and after short-circuiting the organicmemory elements. The organic memory elements of these samples haverepeatability also in voltage that short-circuits each organic memoryelement, and the error is within 0.1 V.

Next, write voltages and characteristics before and after writing of thesamples 1 to 6 are shown in FIG. 31.

In Table 1, a write voltage (V) indicates an applied voltage atshort-circuiting each organic memory element. R(1V) indicates a valueobtained by dividing a current density at applying 1 V to the organicmemory element after writing by a current density at applying 1 V to theorganic memory element before writing. Similarly, R(3V) indicates avalue obtained by dividing a current density at applying 3 V to theorganic memory element after writing by a current density at applying 3V to the organic memory element before writing. Namely, R(1V) and R(3V)indicate changes in current density before and after writing into theorganic memory element. It is determined that the difference in currentdensity of the organic memory element is large, specifically 10 to thefourth power or more, in the case where the applied voltage is 1 V ascompared with the case where the applied voltage is 3V.

Embodiment 6

In the present embodiment, a semiconductor device that has flexibilitywill be described with reference to FIGS. 28A and 28B and FIGS. 29A to29C.

As shown in FIG. 28A, a SiON film 6102 that is 100 nm in film thicknessis formed on a glass substrate 6101 by plasma CVD. Then, as a peelinglayer, a tungsten film 6103 that is 30 nm in film thickness is formed bysputtering. Then, in contact with the tungsten film 6103 as a peelinglayer, a SiO₂ film 6104 that is 200 nm in film thickness is formed bysputtering. A SiNO film 6105 that is 50 nm in film thickness, a SiONfilm 6106 that is 100 nm in film thickness, and an amorphous siliconfilm (not shown in the figure) that is 66 nm in film thickness arecontinuously formed by plasma CVD.

Next, the glass substrate 6101 is heated at 550° C. for 4 hours in anelectric furnace. By the heating, a tungsten oxide layer (not shown inthe figure) is formed at the interface between the tungsten film 6103that serves as a peeling layer and the SiO₂ film 6104. In addition, theamorphous silicon film is crystallized, and a crystalline silicon filmis thus formed.

Next, after dry etching of the crystalline semiconductor film, aconductive layer is formed in such away that a Ti film that is 60 nm infilm thickness, a TiN film that is 40 nm in film thickness, an Al filmthat is 40 nm in film thickness, a Ti film that is 60 nm in filmthickness, and a TiN film that is 40 nm in film thickness are stacked bysputtering. Then, a resist mask is formed by photolithography, and theconductive layer is etched with the resist mask as a protective film toform a wiring 6107.

Next, a Ti film that is 100 nm in film thickness is formed on the wiring6107 and the SiON film 6106 by sputtering. Then, a resist mask is formedby photolithography, and the Ti film is etched by wet etching using HFwith the resist mask as a protective film to form a first conductivelayer 6108.

Next, after a photosensitive is applied and baked to form a polyimidelayer 1.5 μm in film thickness, an insulating layer 6109 covering anedge portion of the first conductive layer 6108 is formed by exposureand development. At this point, a portion of the first conductive layer6108 is exposed. Then, an organic compound layer 6110 that is 30 nm inthickness is formed by evaporation on the insulating layer 6109 and theexposed first conductive layer 6108, here, with the use of NPB. Then, asecond conductive layer 6111 that is 200 nm in thickness is formed byevaporation, here, with the use of aluminum.

Next, an epoxy resin 6112 is applied, and then, baked at 110° C. for 30minutes. Then, a flexible film 6113 is attached to the surface of theepoxy resin 6112. Then, an adhesive tape is attached to the glasssubstrate 6101. Then, the flexible film 6113 is bonded to the epoxyresin 6112 by heating at 120 to 150° C. Then, the glass substrate 6101is disposed on a flat surface, an adhesive roller is attached to thesurface of the flexible film 6113 by pressure bonding, and the layersincluding an organic element are peeled off at the interface (an arrow6114 in FIG. 28A) between the tungsten film 6103 that serves as apeeling layer and the SiO₂ film 6104 (refer to FIG. 28B).

FIGS. 29A to 29C show photographs and a pattern diagram of the organicmemory element thus peeled off from the glass substrate 6101.

FIG. 29A is a photograph of the organic memory element formed over theflexible film 6113, taken from the organic memory element side, that is,form the SiO₂ film side. FIG. 29B is a pattern diagram of FIG. 29A. Thesecond conductive layer 6111, the insulating film 6109, the firstconductive layer 6108 are stacked over the flexible film 6113, and thewiring 6107 connected to the first conductive layer 6108 is formed. Itis to be noted that the organic compound layer 6110 on the surfaces ofthe insulating layer 6109 and the second conductive layer 6111 isindicated by a dashed line. Since the organic compound layer 6110 is notcolored and has a thin film thickness, it is not possible to recognizethe organic compound layer 6110 visually in FIG. 29A or 29C.

FIG. 29C is a photograph of the organic memory element shown in FIG.29A, taken from the flexible film 6113 side.

As described above, a semiconductor device that has flexibility (amemory device or a memory) in which an organic memory element isprovided over a flexible film can be manufactured.

Embodiment 7

In the present embodiment, FIG. 30 shows a result of measuringcurrent-voltage characteristics of an organic memory element for thecase of applying a voltage to first and second conductive layers of theorganic memory element to insulate the organic memory element in orderto carry out writing.

The organic memory element is formed in such a way that the firstconductive layer is formed on a glass substrate by sputtering, thesurface of the first conductive layer is cleaned with apolyvinylalcohol-based porous body to remove dust on the surface, anorganic compound layer that is 20 nm in thickness on the firstconductive layer by evaporation, and the second conductive layer isformed on the organic compound layer by evaporation to be 200 nm inthickness. The first conductive layer, the organic compound layer, andthe second conductive layer are formed by using titanium, Alq₃, andaluminum here, respectively. After that, an epoxy resin is applied andheated for sealing of the organic memory element. In this case, the sizeof the organic memory element in the horizontal plane is made to be 5μm×5 μm.

In FIG. 30, the horizontal axis indicates a voltage, the vertical axisindicates a current value, plots 6301 show a result of measuringcurrent-voltage characteristics of the organic memory element beforewriting data, and plots 6302 show a result of measuring current-voltagecharacteristics of the organic memory element immediately after writing.The write voltage in this case is 12 V, and the write current value is5×10⁻⁴ μA. In addition, the current value decreases immediately afterwriting to be 5×10⁻¹² to 3×10⁻¹¹ μA. This result indicates that data canbe written by applying a voltage, and further, data can be read by achange in the current value of the organic memory element.

This application is based on Japanese Patent Application serial No.2004-303595 field in Japan Patent Office on Oct. 18, 2004, the contentsof which are hereby incorporated by reference.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless such changes andmodifications depart from the scope of the present invention hereinafterdefined, they should be construed as being included therein.

EXPLANATION OF REFERENCE

11: power supply circuit, 12: clock generation circuit, 13: datademodulation/modulation circuit, 14: control circuit, 15: interfacecircuit, 16: memory, 17: data bus, 18: antenna, 19: reader/writer, 20:semiconductor device, 21: memory cell, 22: memory cell array, 23:decoder, 24: decoder, 25: selector, 26: read/write circuit, 27: firstconductive layer, 28: second conductive layer, 29: organic compoundlayer, 30: substrate, 31: flexible substrate, 32: laser lightirradiation means, 33: insulating film, 34: insulating film, 35: groupof elements, 36: substrate, 37: terminal area, 38: substrate, 39:conductive particle, 40: resin, 42: substrate, 43: flexible substrate,44: semiconductor layer, 45: semiconductor layer, 46: resistive element,47: differential amplifier, 51: roll, 52 heating means, 53: controlmeans, 94: display portion, 95: reader/writer, 96: wireless tag, 97:article, 216: memory, 221: memory cell, 222: memory cell array, 223:decoder, 224: decoder, 225: selector, 226: read/write circuit, 232:laser irradiation system, 240: transistor, 241: organic memory element,243: first conductive layer, 244: organic compound layer, 245: secondconductive layer, 246: resistive element, 247: sense amplifier, 248:CMOS circuit, 249: insulating layer, 261: plots, 262: plots, 271: plots,272: plots, 280: substrate, 281: integrated circuit, 282: memory, 1001:laser irradiation system, 1002: PC, 1003: laser oscillator, 1004: powersupply, 1005: optical system, 1006: acousto-optic modulator, 1007:optical system, 1009: moving mechanism, 1011: driver, 1012: driver,1013: autofocus mechanism, 2301: protective layer, 2302: group ofelements, 2303: protective layer, 2304: antenna, 2305: drain electrode,2306: source electrode, 2307: gate electrode, 6001: semiconductordevice, 6002: memory cell array, 6003: portion of column decoder, 6004:portion of row decoder, 6005: read/write circuit, 6007: selector, 6008:selector, 6009: dashed line, 6011: plots, 6012: plots, 6013: plots,6015: plots, 6016: plots, 6017: plots, 6101: glass substrate, 6102: SiONfilm, 6103: tungsten film, 6104: SiO₂ film, 6105: SiNO film, 6106: SiONfilm, 6107: wiring, 6108: first conductive layer, 6109: insulatinglayer, 6110: organic compound layer, 6111: second conductive layer,6113: flexible film, 6114: arrow, 6301: plots, 6302: plots

1. Paper in which a wireless tag is implanted, the wireless tagcomprising: a memory element formed on a flexible substrate; and anantenna formed on the flexible substrate, the antenna being capable ofreceiving and sending electromagnetic field and supplying power foroperating the memory element, wherein the memory element comprises anorganic compound layer disposed between a pair of electrodes.
 2. Thepaper according to claim 1, wherein the memory element is arranged tochange a distance between the pair of electrodes when a voltage isapplied between the pair of electrodes.
 3. The paper according to claim1, wherein the memory element is arranged to change a distance betweenthe pair of electrodes when a voltage is applied between the pair ofelectrodes, and wherein the change in distance between the pair ofelectrodes allows a part of one of the pair of electrodes and a part ofthe other of the pair of electrodes to be brought in contact with eachother.
 4. The paper according to claim 1, wherein the wireless tagfurther comprises a thin film transistor which is electrically connectedto the memory element.
 5. The paper according to claim 1, wherein thepair of electrodes comprises a conductive material selected fromaluminum, copper, silver, and titanium.
 6. An organic resin in which awireless tag is implanted, the wireless tag comprising: a memory elementformed on a flexible substrate; and an antenna formed on the flexiblesubstrate, the antenna being capable of receiving and sendingelectromagnetic field and supplying power for operating the memoryelement, wherein the memory element comprises an organic compound layerdisposed between a pair of electrodes.
 7. The organic resin according toclaim 6, wherein the memory element is arranged to change a distancebetween the pair of electrodes when a voltage is applied between thepair of electrodes.
 8. The organic resin according to claim 6, whereinthe memory element is arranged to change a distance between the pair ofelectrodes when a voltage is applied between the pair of electrodes, andwherein the change in distance between the pair of electrodes allows apart of one of the pair of electrodes and a part of the other of thepair of electrodes to be brought in contact with each other.
 9. Theorganic resin according to claim 6, wherein the wireless tag furthercomprises a thin film transistor which is electrically connected to thememory element.
 10. The organic resin according to claim 6, wherein thepair of electrodes comprises a conductive material selected fromaluminum, copper, silver, and titanium.
 11. A packaging material inwhich a wireless tag is implanted, the wireless tag comprising: a memoryelement formed on a flexible substrate; and an antenna formed on theflexible substrate, the antenna being capable of receiving and sendingelectromagnetic field and supplying power for operating the memoryelement, wherein the memory element comprises an organic compound layerdisposed between a pair of electrodes.
 12. The packaging materialaccording to claim 11, wherein the memory element is arranged to changea distance between the pair of electrodes when a voltage is appliedbetween the pair of electrodes.
 13. The packaging material according toclaim 11, wherein the memory element is arranged to change a distancebetween the pair of electrodes when a voltage is applied between thepair of electrodes, and wherein the change in distance between the pairof electrodes allows a part of one of the pair of electrodes and a partof the other of the pair of electrodes to be brought in contact witheach other.
 14. The packaging material according to claim 11, whereinthe wireless tag further comprises a thin film transistor which iselectrically connected to the memory element.
 15. The packaging materialaccording to claim 11, wherein the pair of electrodes comprises aconductive material selected from aluminum, copper, silver, andtitanium.
 16. A certificate in which a wireless tag is implanted, thewireless tag comprising: a memory element formed on a flexiblesubstrate; and an antenna formed on the flexible substrate, the antennabeing capable of receiving and sending electromagnetic field andsupplying power for operating the memory element, wherein the memoryelement comprises an organic compound layer disposed between a pair ofelectrodes.
 17. The certificate according to claim 16, wherein thememory element is arranged to change a distance between the pair ofelectrodes when a voltage is applied between the pair of electrodes. 18.The certificate according to claim 16, wherein the memory element isarranged to change a distance between the pair of electrodes when avoltage is applied between the pair of electrodes, and wherein thechange in distance between the pair of electrodes allows a part of oneof the pair of electrodes and a part of the other of the pair ofelectrodes to be brought in contact with each other.
 19. The certificateaccording to claim 16, wherein the wireless tag further comprises a thinfilm transistor which is electrically connected to the memory element.20. The certificate according to claim 16, wherein the pair ofelectrodes comprises a conductive material selected from aluminum,copper, silver, and titanium.
 21. Paper money in which a wireless tag isimplanted, the wireless tag comprising: a memory element formed on aflexible substrate; and an antenna formed on the flexible substrate, theantenna being capable of receiving and sending electromagnetic field andsupplying power for operating the memory element, wherein the memoryelement comprises an organic compound layer disposed between a pair ofelectrodes.
 22. The paper money according to claim 21, wherein thememory element is arranged to change a distance between the pair ofelectrodes when a voltage is applied between the pair of electrodes. 23.The paper money according to claim 21, wherein the memory element isarranged to change a distance between the pair of electrodes when avoltage is applied between the pair of electrodes, and wherein thechange in distance between the pair of electrodes allows a part of oneof the pair of electrodes and a part of the other of the pair ofelectrodes to be brought in contact with each other.
 24. The paper moneyaccording to claim 21, wherein the wireless tag further comprises a thinfilm transistor which is electrically connected to the memory element.25. The paper money according to claim 21, wherein the pair ofelectrodes comprises a conductive material selected from aluminum,copper, silver, and titanium.
 26. Securities in which a wireless tag isimplanted, the wireless tag comprising: a memory element formed on aflexible substrate; and an antenna formed on the flexible substrate, theantenna being capable of receiving and sending electromagnetic field andsupplying power for operating the memory element, wherein the memoryelement comprises an organic compound layer disposed between a pair ofelectrodes.
 27. The securities according to claim 26, wherein the memoryelement is arranged to change a distance between the pair of electrodeswhen a voltage is applied between the pair of electrodes.
 28. Thesecurities according to claim 26, wherein the memory element is arrangedto change a distance between the pair of electrodes when a voltage isapplied between the pair of electrodes, and wherein the change indistance between the pair of electrodes allows a part of one of the pairof electrodes and a part of the other of the pair of electrodes to bebrought in contact with each other.
 29. The securities according toclaim 26, wherein the wireless tag further comprises a thin filmtransistor which is electrically connected to the memory element. 30.The securities according to claim 26, wherein the pair of electrodescomprises a conductive material selected from aluminum, copper, silver,and titanium.
 31. A method to prevent user from falsifying an article,the method comprising a step of providing a wireless tag to the article,wherein the wireless tag comprises: a memory element formed on aflexible substrate; and an antenna formed on the flexible substrate, theantenna being capable of receiving and sending electromagnetic field andsupplying power for operating the memory element, wherein the memoryelement comprises an organic compound layer disposed between a pair ofelectrodes.
 32. The method according to claim 31, wherein the memoryelement is arranged to change a distance between the pair of electrodeswhen a voltage is applied between the pair of electrodes.
 33. The methodaccording to claim 31, wherein the memory element is arranged to changea distance between the pair of electrodes when a voltage is appliedbetween the pair of electrodes, and wherein the change in distancebetween the pair of electrodes allows a part of one of the pair ofelectrodes and a part of the other of the pair of electrodes to bebrought in contact with each other.
 34. The method according to claim31, wherein the wireless tag further comprises a thin film transistorwhich is electrically connected to the memory element.
 35. The methodaccording to claim 31, wherein the pair of electrodes comprises aconductive material selected from aluminum, copper, silver, andtitanium.
 36. The method according to claim 31, wherein the article isselected from a bill, a coin, a security, a certificate, a container forwrapping, a book, a storage medium, a vehicle, a grocery, and a garment.